1. Field of the Invention
The present invention relates to a light emissive panel unit used as a surface light source unit and a display panel unit.
2. Description of the Related Art
FIG. 1 shows a conventional surface light source unit disclosed in Japanese Laid Open Patent Application No. 2-157791. Referring to FIG. 1, a surface light source unit 10 has a plate body 11 and cold-cathode lamps 12 facing side edge surfaces of the plate body 11. The plate body 11 has a light guide plate 13 made of acrylic resin, a light diffusing plate 14 and a reflecting plate 16. The light diffusing plate 14 is provided on a surface of the light guide plate 13. The reflecting plate 16 is provided with a diffusive reflecting layer 15 formed on a surface thereof. The reflecting plate 16 is provided on another surface of the light guide plate 13 such that the diffusive reflecting layer 15 is on the surface of the light guide plate.
In the surface light source unit shown in FIG. 1, light emitted from the cold-cathode lamps 12 is shut into the light guide plate 13 and is repeatedly reflected by the diffusive reflecting layer 15 and the boundary between the surface of the light guide plate 13 and the light diffusing plate 14. While the light is being repeatedly reflected, a part of the light shut in the light guide plate 13 is emitted through the light diffusing plate 14. As a result, the surface of the diffusing plate 14 uniformly lights.
The conventional surface light source unit described above must have the light guide plate 13 which is solid. Thus, the surface light source unit is relatively heavy. In addition, it is difficult to adjust the brightness of the surface light source unit.